Histograms illustrating the DNA content of MK produced from diploid CD34⁺CD41⁺ cells after culture with various cytokines. (A) Cells cultured with TPO. (B) Cells cultured with IL-3. (C) Cells cultured with TPO and IL-3. (D) Cells cultured with SCF and IL-6. All cultures were performed in serum-free media and harvested after 7 days. The histograms shown are all from the same experiment to facilitate comparison but are representative of the results obtained in two to five experiments. The data were obtained by electronically gating on PI-stained, CD41⁺ cells after eliminating dead cells and debris by gating on forward and right angle scatter.